I usually get supplies from small business owners (try Far East Plaza). So I can still have nice looking nails during periods when I have to save money. If you are being frugal, you can just get the basics done at the Salon/Spa and do the extras yourself, like I do =)
For example, a bottle of acrylic solution costs $40 but is good for 5 sessions. At $60 per soak off, I save $260 by doing it myself.
Sometimes, it is also about control. By having my own drill, UV lamp and other materials, I will no longer be subject to the Spa's schedule. Overbooking during festive seasons will no longer be an issue =P